U.  S.  DEPARTMENT  OF  AGRICULTURE, 

BUREAU   OF  ENTOMOLOGY— CIRCULAR  No.  152. 

L.  O.  HOWARD.  Entomologist  and  Chief  of  Bureau. 


THE  RICE  WATER-WEEVIL  AND  METHODS 
FOR  ITS  CONTROL. 


E.  S.  TUCKER, 
Entomological  Assistant. 


WASHINGTON':    GOVEIINMEN1     PRINTING    OFFICE: 


BUREAU  OF  EXTOMOLOGY. 

L.  O.  Howard,  Entomologist  and  Chief  of  Bureau. 

C.  L.  Marlatt.  Entotnologist  and  Acting  Chief  in  Absence  of  Chief. 

R.  S.  Clifton,  Executive  Assistant. 

W.  F.  Tastet.  Chief  Clerk. 

F.  H.  Chittenden,  in  charge  of  truck  crop  and  stored  product  inst  ct  investigations. 

A.  D.  Hopkins,  in  charge  of  forest  insect  investigations. 

W.  I>.  Hunter,  in  charge  of  southern  field  crop  insect  investigations. 

V.  M.  Webster,  in  (lunge  of  cereal  and  forage  insect  investigations. 

A.  L.  Qitaintance,  hi  charge  of  deciduous  [mil  insect  investigations. 

E.  F.  Phillips,  in  charge  of  bee  culture. 

T>.  M.  Rogers,  in  charge  of  prev<  nting  spread  of  moths,  fit  Id  work. 
Rolla  I\  Currie,  in  charge  of  editorial  work. 
Mabel  Colcord.  in  charge  of  library. 

Southern  Field  Crop  Insect  Investigations. 

\Y.  D.  Hunter.  in  charge. 

W.  D.  Pierce,  G.  D.  Smith,  J.  D.  Mitchell,  Harry  Pinkus,  B.  R.  Coad,  R.  "W. 
Moreland,  engaged  in  cotton-boll  weevil  investigations. 

F.  C.  Bishopp,  A.  II.  Jennings,  H.  P.  Wood,  W.  V.  King,  engaged  in  tick  investi- 
gations. 

A.  C.  Morgan,  G.  A.  Runner,  S.  E.  Crumb,  D.  C.  I'arman,  engaged  in  tobacco 

insect  investigations. 
T.  E.  Holloway.  E.  R.  P.ariser,  engaged  in  sugar  cam-  insect  investigations. 
E.  A.  McGregor,  W.  A.  Thomas,  <  ngag<  d  in  red  spider  and  other  cotton  insect 

investigations. 
J.  L.  Webb,  engaged  in  rice  inset  investigations. 

11.  A.  Cooley,  1  >.  L.  Van  Dine,  A.  F.  Conbadi,  C.  C.  Kbumbhaar,  collaborators. 
ii 


Circular  No.  152. 

United  States  Department  of  Agriculture, 

BUREAU   OF  ENTOMOLOGY. 
L.  O.   HOWARD,  Entomologist  and   Chief  of  Bureau. 


THE  KICK  WATKIMVKKVIL  AND  METHODS  FOR  ITS 

CONTROL. 

i  Lissorhoptrus  simplex  Say.) 

By  E.  S.  Tuckj  R, 
tomological  Assistant. 

ECONOMIC  1  M  PORTANCE. 

The  most  serious  insect  enemy  of  growing  rice  in  the  Southern 
States  i-  tlic  rice  water-weevil  (Lissorhoptrus  simplex  Say)  (fig.  1). 
When  in  its  larval  stage,  the  insect  is  known  to  rice  growers  as  the 
■•  rice  root-maggot/'  The  larvae  feed  on  the  roots  of  rice  plants,  and 
the  adult  weevils  cause  some  harm  by  feeding  on  rice  leave-. 

Owing  to  the  extensive  growing  of  rice  in  sections  of  Louisiana, 
Texas,  and  Arkansas  within  recent  years,  the  weevil  has  found  very 
favorable  condition-  in  the  rice  fields  for  its  multiplication  in  propor- 
tion to  the  increase  of  the  acreage  and  to  the  number  of  year-  in 
which  rice  ha-  been  grown  in  any  section.  The  development  of 
definite  rice-growing  areas  in  these  States  ha-  naturally  resulted  in 
particular  center-  of  high  infestation  by  the  weevil.  Rice  growing 
has  consequently  been  attended  by  great  damage  to  (he  crop-  on 
.e  count  of  the  insect's  attacks. 

Tin  amount  of  loss  that  is  occasioned  by  the  attacks  i-.  difficult  to 
estimate,  a-  the  reduction  of  yield  has  been  variously  reckoned  in 
different  localities.  Since  all  fields  are  not  affected  alike  and  differ- 
ent portions  or  spots  of  a  held  are  apt  to  suffer  the  severest  injuries, 
although  the  plants  seldom  fail  outright,  the  growers  differ  much 
in  their  opinion.-  of  ill-  extent  of  damage  which  they  sustain,  hut  all 
e  in  the  declaration  that  it  is  considerable.  General  statements 
of  the  shortage  of  production  include  a  report  by  a  grower  at  Beau- 
:.  Tex.,  who  placed  his  loss  a-  low  as  1  per  cent  :  hut  the  attacks 
in  '.me  fields  at  Stuttgart,  Ark.,  have  been  severe  enough  to  cut 
down  the  yield  a-  much  as  75  per  cent. 

1 


THE    KICK    WATER-WEEVIL, 


Pig.   I.    -The  rice  water-weevil   (Lissorhoptrua  simplex)  :  a,  Rice  plant  showing  Injuries; 

h,  larval   scars   on  section   of  root:    c,   section   of   rootlet    showing   feeding  scars:    d, 
water  line;  e,  c,  c,  roots  severed  by  larva-;  /,  Injured  leaf;  /',  enlarged  section  of  injured 
leaf;  y,  adult  beetle,  dorsal  view,  much  enlarged;  h,  antenna  of  beetle,  more  enls 
i,   larva,   side   view,    much   enlarged ;    /.   enlarged    segment    of  larva,   lateral   view ;   k, 
dorsal  structure  of  larva.      (Original.  I 


i  ii  i i  RK  i     w  \  i  i  i;  w  i  t'.viL.  8 

The  recent  work  of  the  bureau  on  the  rice  water-weevi]  was  begun 
in  L910  ly  Mi-.  ('.  E.  Hood,  working  under  the  direction  of  Mr.  D.  L. 
Van  Dine.  The  present  writer  began  work  on  the  problem  in  1911. 
In  this  circular  many  notes  made  by  Mr.  Hood  arc  incorporated. 

The  object  of  this  paper  is  to  give  as  much  practical  information 
as  is  h<>\\  available  about  the  weevil  and  measures  for  its  control  in 
order  that  rice  growers  may  make  proper  efforts  in  fighting  the  pest 
and  secure  larger  crops.  The  cooperative  facilities  afforded  by  the 
A.gricultural  Experiment  Station  of  Louisiana,  through  Prof.  W.  R, 
Dodson,  director,  in  providing  accommodations  at  the  State  Rice 
Station.  Crowley,  La.,  and  allowing  free  use  of  the  unpublished  notes 
comprising  a  preliminary  investigation  of  the  rice  water-weevi]  by 
Mr.  Wilmon  Newell,  in  L909,  deserve  grateful  acknowledgment. 

HISTORICAL  ACCOT  XT  ANT)  DISTRIBI  TION. 

The  weevil  was  originally  described  in  ]<'<\  as  Bagous  simplex 
by  Thomas  Say.  It  and  another  species  of  weevil  were  given  the 
generic  name  of  Lissorhoptrus  by  Dr.  J.  L.  LeConte  in  L876.  Le- 
Conte  and  Horn  have  stated  thai  the  weevil  commonly  inhabits 
swampy  place-  throughout  the  eastern  part  of  the  United  States. 
Its  northern  range  extends  into  the  Lower  Peninsula  of  Michigan, 
according  to  Hubbard  and  Schwarz,  and  Dury  has  recorded  the  spe- 
cie- as  being  taken  near  Cincinnati.  Ohio.  It  is  also  reported  from 
New  Jersey,  Maryland,  and  the  District  of  Columbia.  Mr.  E.  A. 
Schwarz  has  concluded  "  that  t  he  genus  Lissorhoptrus  occurs  all  along 
the  Atlantic  coast  (including  the  Gulf  of  Mexico),  recur-  along  the 
Great  Lakes,  and  i-  occasionally  found  inland." 

A-  an  injurious  insect,  the  species  first  attracted  the  attention  of 
rice  farmers  along  the  Savannah  River  in  Georgia  and  South  Caro- 
lina. In  1881  Dr.  L.  ().  Howard  visited  a  rice  plantation  known  as 
"  Proctor's,"  and  owned  by  (  ol.  John  Screven,  on  the  South  Carolina 
side  of  the  river,  a  short  distance  below  Savannah,  Ga.,  for  the  pur- 
pose of  studying  the  insects  affecting  rice  crops.  An  account  of  his 
observations,  including  notes  on  the  rice  water-weevil,  was  published 
in  the  report  of  the  United  Stale-  Commissioner  of  Agriculture  for 
1881  and  1882.  But  little  advance  has  been  made  in  further  knowl- 
edge of  rice-crop  insects  up  to  the  present  investigation. 

DESCRIPTIONS    O]     STAGES. 

The  adult. — The  mature  insect  is  a  small,  dark-gray  weevil  i  fig. 
1,  g).  The  technical  description  by  Mr.  E.  A.  Schwarz  in  the  account 
above  ment  toned  is  here  quot<  d  : 

Lissorhoptrus  simplex.-  [mago:  Average  length  from  tip  of  thorax,  3  mm. 
Oblong-oval,  covered   with   large,  dirt-colored   scales,  bul    usually  entirely  en- 


4  THE    RICE    WATEE-WEEVTL. 

veloped  ill  an  argillaceous  coating,  which  renders  scales  and  sculpture  irrecog- 
Dizable.  Rostrum  stout,  as  long  as  head  and  thorax,  subeylindrical,  densely 
rugosely  punctulate,  neither  sulcate  nor  carinate;  head  densely  punctulate. 
Thorax  as  long  as  wide,  constricted  anteriorly,  lateral  lobes  well  developed, 
sides  moderately  rounded,  base  truncate,  a  finely  impressed  median  line,  sur- 
face densely  rugosely  punctate,  sides  at  middle  with  a  shallow  transverse  im- 
pression. Elytra  much  wider  at  base  than  thorax  and  about  twice  as  lung: 
humeri  oblique,  strongly  declivous  at  apex,  punctate-striate,  interstices  wide, 
subconvex,  3d  and  5th  more  prominent  at  declivity  than  the  rest.  Presternum 
flattened,  transversely  impressed  in  front  of  coxae;  abdomen  coarsely  punctate. 
Tibiae  somewhat  curved,  armed  with  a  strong  terminal  book;  tarsi  narrow. 
third  joint  not  emarginate;  claws  slender,  approximate. 

Very  little  difference  exists  between  the  sexes.  The  females  usually 
have  a  slightly  larger  body  than  the  males,  and  are  often  more  dis- 
tinctly marked  with  a  black  area  on  the  back.  The  marks  of  colora- 
tion, however,  show  more  plainly  on  live  moistened  specimens  in  the 
field  than  on  dry  examples  either  alive  or  dead.  According  to  Mr. 
W.  D.  Pierce,  a  secondary  sexual  character  is  presented  by  the  con- 
figuration of  the  scrobe  on  the  beak.  He  has  determined  that  the 
scrobe  of  the  female  is  slightly  curved,  but  in  the  male  it  is  practi- 
cally straight.  These  fine  distinctions  are  difficult  to  make  out  with 
certainty  on  account  of  the  natural  curvature  of  the  beak. 

The  pupa. — No  example  of  the  pupa  fit  for  description  has  yet  been 
obtained,  as  it  is  very  soft  and  any  slight  pressure  or  touch  that  is  ex- 
erted in  attempting  to  remove  one  from  the  mud  crushes  or  distorts  it. 

The  egg. — All  attempts  to  secure  deposited  eggs  have  afforded  only 
partial  results.  For  purposes  of  description  dependence  must  at 
present  be  placed  upon  the  appearance  of  eggs  obtained  by  dissection 
of  gravid  female  weevils.  Mr.  Wilmon  Newell,  in  presenting  a  de- 
scription based  upon  such  observations,  has  stated  that  the  egg  is 
pure  white,  cjdindrical  and  slightly  curved  in  form,  and  has  a  length 
about  five  times  the  diameter.     It  is  barely  visible  to  the  naked  eye. 

LIFE    HISTORY. 
SEMIAQTJATIC    HABITS. 

Water  is  an  element  in  which  the  weei  il  delights.  It  swims  readily 
on  or  beneath  the  surface,  and  it  feeds,  rests,  and  mates  almost  as  fre- 
quently in  the  water  as  above  it.  To  determine  how  long  the  adults 
can  live  under  water,  Mr.  C.  E.  Hood  conducted  a  test  in  which  one 
weevil  died  after  passing  the  first  24  hours  of  submersion,  but  two 
did  not  die  until  after  being  kepi  submerged  for  fully  96  hours.  The 
weevil  does  not  carry  a  bubble  of  air  for  breathing  purposes  when  it 
goei  below  the  surface,  although  tiny  globules  of  air  are  apt  to  adhere 
to  parts  of  the  body.  Without  water,  the  insect  can  not  breed.  The 
eggs  arc  probably  deposited  on  roots  under  water  or  in  mud,  and  the 


THE    RICE    w  A  III:   w  EEVIL. 


larva,  and  doubtless  also  the  pupa,  require  a  bed  of  saturated  earth  in 
which  to  live.     Wet  conditions  of  soil  with  suitable  vegetation  a] 
to  be  ry  for  the  development  of  all  the  stages. 


I  OOD    I'l    Wlv 


The  semiaquatic  life  of  the  insecl  demands  thai  its  proper  food 
plants  be  adapted  for  growing  in  moist  situations  or  entirely  in 
water.  The  adult  weevil  itself  is  not  disposed  to  feed  on  any  plant 
unless  the  roots  are  at  leasl  partially  covered  with  water  or  soft  mud. 
In  South  Carolina  Dr.  Howard  observed  weevils  feeding  on  "  Sagit- 
taria.  Scirpus,  Cyperus,  Nymphsea,  and  Nuphar"  -plants  commonly 
known  as  arrowhead,  bulrush,  galingale,  water  lily,  and  spatter-dock. 
Besides  these,  he  reported  wild  rice  (Zizarda  aquatica)  as  well  as 
cultivated  rice  (Orysa  sativa).  One  specimen  has  been  collected  as  a 
visitor  on  Baptisia  at  Victoria,  Tex.  All  positive  records  of  addi- 
tional food  plant-  refer  entirely  to  grasses  and  they  are  the  result  of 
observations  that  were  mostly  made  in  Louisiana.  Mr.  Hood  has  re- 
ported some  of  the  Louisiana  grasses  by  the  common  name-  of  "bull 
grass"  and  "nigger's  wool."  which  grew  at  Crowley.  ••Hurrah 
grass"  was  recorded  by  Mr.  D.  L.  Van  Dine  at  Matagorda,  Tex. 
Adult  wee\  Lis  U'^\  on  the  leaves  of  these  undetermined  grasses  and  the 
larva'  were  found  on  the  root-  of  the  first,  winch  was  identified  by 
the  writer  as  a  Paspalum  ami  was  -aid  to  have  been  introduced  into 
the  count  ry.  "  Bull  grass '"  is  a  very  common  term  in  the  section  and 
refers  to  several  specii  -  of  grasses. 

The  occurrence  of  weevils  on  Walter's  swale  grass  {Paspalum 
membranaceum)  was  first  observed  by  Mr.  Newell  at  Hake  Arthur, 
La.  "While  similar  observations  have  been  made  by  the  writer  at 
Crowley.  I. a.,  and  Tine  Bluff,  Ark.,  the  finding  of  larvae  on  the  roots 
of  the  grass  at  ( 'row  ley  presented  complete  e\  idence  of  the  true  host 
relation-hip  of  the  plant.  This  fact,  however,  may  have  been  dis- 
covered ly  Mr.  Newel]  two  years  previously  at  the  same  place  where 
he  found  larvae  infesting  tie  root-  of  a  stocky  Paspalum,  which  he  was 
inclined  to  regard  a-  another  species. 

Al-o  during  the  season  of  1911,  at  Crowley.  La.,  the  writer  found 
two  other  species  of  grass  which  attracted  the  weevils  from  the 
nearest  rice  plant-.  One  of  these  was  Bermuda  grass  (Capriola 
dactylon).  It  grew  on  a  levee  in  a  rice  field  which  had  become  partly 
overflowed  with  the  flood  water.  A-  an  attempt  hail  been  made  to 
grow  it  on  the  land  previous  to  the  rice  crop,  it-  occurrence  under 
•flooded  condition-  was  exceptional,  and  no  larva?  were  found  attack- 
ing the  root,.  It  can  not  lie  considered  a-  a  proper  host  plant.  In 
the  other  case,  a  hunch  of  "  water  crab  grass,"  undoubtedly  a  species 
of   Syntherisina.    was   making   a    desperate   struggle    for   existence 


6  THE   RICE   WATER-WEEVIL. 

within  a  flooded  rice  field.  Having  evidently  started  into  growth 
before  the  field  became  irrigated,  this  crab  grass  was  able  to  live  in  a 
depth  of  about  C  inches  of  water.  Xot  only  were  the  leaves  severely 
fed  upon  by  weevils,  but  the  roots  were  attacked  by  larvae. 

APPEARANCE    OF    ADULTS    IN    RICE    FIELDS. 

Since  the  growing  of  rice  offers  special  inducements  for  the  breeding 
of  the  weevil,  clue  to  the  attraction  of  the  plants  and  the  wet  condi- 
tions which  they  demand  for  growth,  rice  has  become  the  favorite 
food  plant  of  the  insect.  Directly  after  the  rice  fields  are  flooded 
the  weevils  appear  and  commence  feeding  on  the  leaves  of  the  young 
plants.  In  southern  Louisiana,  where  much  of  the  water  is  supplied 
by  canals,  the  irrigation  of  rice  fields  usually  begins  in  the  first  week 
of  May,  but  the  time  of  turning  on  water  in  different  fields  is  often 
later,  the  flooding  sometimes  not  being  clone  until  in  July  to  accord 
with  late  planting.  "Where  water  is  pumped  onto  the  fields:  a  steady 
flow  must  be  maintained  for  several  clays  before  any  large  area  of  land 
can  be  inundated.  The  flooding  of  fields  in  Arkansas  is  not  generally 
effected  earlier  than  the  middle  of  June. 

By  following  the  application  of  water  in  every  field  the  weevils 
gather  most  numerously  on  plants  that  stand  in  the  depressions  and 
lower  portions  having  the  deepest  flood.  Mr.  Hood  has  counted  as 
many  as  18  weevils  on  a  stool  and  12  on  a  single  plant.  An  average 
of  at  least  1  weevil  to  every  5  or  G  plants  in  one  field  has  been 
reckoned  by  Mr.  Newell.  Some  inclination  to  avoid  direct  sunlight 
during  clays  of  hot  weather  is  shown  by  the  weevils,  as  they  seem  to 
prefer  positions  in  the  shade  of  the  plants  and  under  the  surface  of 
the  water. 

They  are  rather  sluggish  except  when  swimming  and  are  disposed 
to  feign  death  if  taken  in  the  hand.  They  show  no  inclination  to 
fly  during  the  day  and  even  refuse  to  expand  the  wings  on  being 
tossed  into  the  air.  Passage  between  separate  plants  is  accomplished 
in  the  daytime  by  swimming.  That  they  can  fly  for  long  distances, 
however,  is  clearly  proven  by  their  attraction  to  artificial  lights  at 
night.  This  propensity  will  be  more  fully  discussed  with  reference 
to  methods  of  control.  Invasion  of  fields  must  therefore  lie  con- 
summated at  night. 

NATURE   OF    ATTACKS    BY    AIM  I   I  S. 

K'ice  is  attacked  in  the  same  manner  as  other  similar  host  plants 
and  the  effects  of  the  feeding  by  the  adults  are  soon  manifested  by 
the  appearance  of  scars  on  the  leaves.  (Fig.  1,  /.)  In  the  act  of  feed- 
ing, the  weevil  braces  its  body  firmly  on  the  upper  side  of  a  leaf,  and 
moving  slowly  forward  in  a  longitudinal  direction  either  up  or  down 
the  blade,  it  chews  out  the  epidermis  and  produces  a  scar,  leaving 


THE    RICE    w  \  I  I  i;   w  EEVIL.  / 

the  underside  uneaten.  These  scars  are  very  narrow,  being  in  fact 
no  wi.lri-  than  the  spread  of  the  mandibles,  but  they  vary  in  length 
from  a  small  fraction  of  an  inch  to  more  than  -J  inches,  depending 
on  the  lime  in  which  the  insect  engages  in  feeding.  When  the  thin 
un.lri--i.lr  dries  within  the  -car.  it  splits  and  forms  an  open  groove 
throughout  the  injured  space.  The  leaves  suffer  no  serious  ill  effects 
from  being  fed  upon  unless  the  scars  become  numerous  enough  Lo 
cause  wilting  and  dying.  A.dults  prefer  tender  young  plants  rather 
than  the  coarser  strong  growth. 

\i  \  1 1  ng    \m>  ovrrosn  ion. 

Throughoul  the  period  in  which  the  weevils  remain  in  evidence, 
mating  take-  plan-  on  nearly  all  occasions  when  a  male  and  female 
happen  to  meet,  and  this  usually  occurs  on  a  leal'.  The  gravid 
females  crawl  down  the  stems  of  the  plants  and  evidently  deposit 
their  eggs  singly  in  a  puncture  that  i<  first  gnawed  in  a  root.  Mr. 
Newell  ha-  mentioned  that  he  has  seen  adult  weevils  which  he  be- 
lieved to  be  females  make  punctures  on  the  stems  below  the  water 
line.  Mr.  Hood  and  the  writer  have  watched  the  operations  of 
lies  when  they  apparently  undertook  to  oviposit  on  rice  roots 
within  glass  tubes.  Each  weevil  thus  observed  deliberately  sought 
out  a  place  on  a  root  anil  ate  into  it  for  about  a  minute.  Then  she 
reversed  her  body,  gripped  tightly,  and  pressed  the  tip  of  the  i 
men  over  the  hole  which  she  had  eaten  out.  Mr.  Hood  has  recorded 
that  he  saw  the  ovipositor  in  the  form  of  a  brown  tubular  organ  in- 
serted into  the  hole.  In  this  case  the  weevil  remained  in  position 
without  any  apparent  movement  for  50  seconds  before  the  ovipositor 
w.i-  withdrawn.  The  writer  ha-  not  been  able  to  -re  the  ovipositor 
extended  nor  t..  detect  an  egg  with  certainty.  The  weevil  may  climb 
up  above  the  water  after  each  operation  and  rest  for  a  long  or  shorl 
I.  ..i-  continue  her  actions  among  the  root-  for  a  while.  One 
weevil  stayed  among  the  root-  for  I".  minutes. 

The  de\  ice  that  was  designed  and  u-ed  by  the  writer  for  observing 
the  method  of  oviposition  by  the  weevils  is  illustrated  in  figure  2. 
In  it-  construction  a  long  lamp  chimney  was  placed  upright  in  a 
saucer  and  cemented  at  the  base  with  plaster  of  Paris.  A  wire  sup- 
port with  the  top  bent  into  a  loop  of  the  proper  size  for  steadying  a 
closed-bottom  glass  tube,  one  with  an  inch  diameter  being  used  to 
hold  the  tool-  of  a  young  rice  plant  in  water,  was  first  placed  in  the 
center  of  the  saucer.  The  lower  end  of  the  support  was  also  bent  in 
iral  to  secure  firmness  after  being  set  in  the  plaster.  By  means 
of  a  string  tied  to  tli,  upper  part  of  the  tube,  it  could  be  lowered 
through  the  top  of  the  chimney  into  a  standing  position  within  the 
wire  loop  and  also  removed  to  permit  close  inspection  of  roots  and 
insects  inside  of  it  whenever  desired. 

I  'ir.  In2     12         2 


8 


THE   RICE    WATER-WEEVIL, 


NATURE    OF     ATTACKS    BY    LARV.E. 


"Sir.  Hood  has  stated  that  the  larvae  are  first  found  in  the  rice  fields 
from  one   to   three   weeks   after  the  turning  on   of  the   water,  the 

time  of  their  inception  varying 
with  the  weather.  Hot  weather 
accelerates  their  development. 
The  young  larva?,  which  have 
doubtless  hatched  from  egg-  laid 
in  the  roots,  begin  to  feed  on 
them,  and  in  course  of  time  as 
the  larvae  increase  in  size  they 
devour  or  sever  large  portions 
of  the  root  system.  They  have 
been  known  to  eat  holes  in  large 
rice  roots  and  burrow  into  them. 
Mr.  W.  D.  Pierce,  at  Beaumont, 
Tex.,  in  1904,  found  vigorous 
larva1  consuming  the  entire  in- 
terior of  the  roots.  Figure  1. 
'.  gives  a  representation  of  Qix 
feeding  holes  made  at  a  distance 
not  more  than  one-fourth  of  an 
inch  apart  as  Mr.  Hood  viewed 
them.  The  common  methods  of 
attack  result  in  a  pruning  of  the 
roots,  after  which  the  severed 
portions  rot  and  the  remaining 
parts  are  further  marred  with 
feeding  -ear-.  At  this  stage  the 
hold  of  the  plant  upon  the  soil 
is  greatly  weakened  and  it  can 
be  pulled  from  the  ground  with 
ea-e.  In  some  instances  on  rec- 
ord the  root  systems  were  en- 
tirely destroyed  and  the  rice 
plants  floated  in  the  water. 

The  injuries  done  by  the  larva; 

first   cause  the  leaves  of  the  rice 

plants  to  turn  a  pale  yellow  and 

droop,    the    lower    blades    often 

re-ting     on     the     water.       With 

severe  attacks  some  of  the  leaves  may  die.    These  effects  in  the  fields 

become  most   pronounced  on  plants  growing  in  depressions  and  low 

portions  of  the  land  into  which  tin'  water  first   flowed  and  where  it 


Fn;.  2. — Lamp-chimney  case  for  rearing 
and  observing  the  rice  water-weevil:  n, 
<;ia-s  lamp  chimney ;  '*.  vessel  containing 
plaster  of  Paris;  <■.  glass  tube;  </.  wire 
support;  c,  rice  plain  :  /.  string  lift  :  g, 
gauze;  h,  rubber  band;  i,  ;',  beetles  feed- 
ing.   (Original.) 


•  I     u  \  I  I  l;   w  !  i  VIL.  9 

stands  deepest.  As  previously  mentioned,  such  places  are  most 
attractive  to  the  adults.  Where  the  adults  occur  most  numerously 
the  larvae  must  be  expected  to  follow  in  great  number.  In  conse- 
quence the  severity  of  the  larval  infestations  is  shown  by  a  yellow 
cast  of  the  leaves  extending  in  broad  streaks  along  dead  furrows, 
while  spots  and  areas  of  yellowish  plants  also  become  visibly  ap- 
parent within  the  hollows  and  sinks  of  the  land.  These  signs  of 
injury  have  appeared  in  fields  after  20  days  of  flooding,  hut  ordi- 
narily the  larvae  do  not  become  numerous  enough  to  cause  much 
damage  until  the  water  has  stood  for  at  least  a  month. 

If  iiian\  of  the  roots  are  cut  off  from  a  plant  (fig.  l.  <  ).  it-  growth 
is  stunted,  but  as  the  growing  rice  plant  possesses  a  strong  vital  power 
new  nuits  are  put  out  to  replace  the  ones  destroyed,  and  on  the  cessa- 
tion of  attacks  the  injured  plant  revives,  or  is  said  to  "recover," 
and  make-  a  belated  growth,  usually  resulting  in  late  heading.  Much 
of  the  unequal  growth  of  the  plants  in  the  fields,  as  well  as  the  irreg- 
ular maturity  of  heads,  is  accountable  to  the  detrimental  effects  of 
the  larval  attacks.  Harvesting  must  necessarily  be  delayed  until  all 
the  heads  are  ripe,  thus  involving  the  risk  of  loss  to  the  normal  yield 
from  storms  or  other  causes. 

Furthermore,  the  attack-  on  the  roots  of  tender  young  plants  pre- 
vent proper  stooling  or  production  of  stems.  In  comparison  with 
normal  plant-,  often  less  than  half  as  many  stems  grow  from  a  stool 
that  has  suffered  damage.  Shortage  of  heads  is  therefore  caused  by 
the  failun  of  badly  injured  plants  to  produce  a  full  quota  of  stems. 
The  fact  that  the  larvae  are  largely  responsible  for  a  great  deficiency 
of  yield  in  this  respect  will  impress  a  comprehension  of  the  amount 
of  loss  caused  by  the  insect . 

DEVEl  OPM1  NT    01     ST  \'.l  s. 

The  length  of  time  required  for  the  development  of  the  weevil 
from  a  freshly  laid  egg  has  been  estimated  by  Mr.  Hood  to  be  about 
Hi  weeks.    Judging  from  the  first  occurrence  of  larvae  in  fields  after 

1     to    3    week-    of    flooding,    a     period     nol     to    exceed     10    day-    would 

probably  be  ample  time  for  an  egg  to  hatch  subsequent  to  deposition. 
Development  is  hastened  with  the  advance  of  hot  weather  when  the 
ater  and  soil  become  warm.     Usually  nol  until  about  six  or 

-  after  flooding  do  many  of  the  larva?  attain  full  growth  and 
appear  ready  for  pupation,  although  pupa'  have  been  found  in  a  field 
that  at  the  time  had  been  irrigated  for  only  five  week-.  In  prepara- 
tion for  the  pupal  stage  the  larva  form-  a  cell  in  the  mud  among  the 
or  at  the  tip  of  one.  and  Mr.  Hood  has  asserted  that  the  pupa 
passes  two  .ir  three  week-  before  it  matures  and  the  i  ce  of  the 

adult    take-   pl.e  i 


10  THE   RICE    WATER-WEEVILi. 

With  the  aim  of  working  out  the  details  of  development  of  the 
larval  and  pupal  stages,  a  number  of  larvae  were  placed  on  the  roots 
of  young  rice  plants,  each  of  which  was  set  in  water  within  a  glass 
tube,  the  tubes  being  simply  stood  in  a  holder.  Attempts  to  carry 
through  the  development  of  pupae  from  larvae  when  subjected  to  con- 
stant exposure  to  light  proved  only  partially  successful,  but  better 
progress,  although  still  lacking  completeness,  was  made  after  shield- 
ing the  tubes  from  light  and  supplying  a  small  amount  of  earth  with 
the  roots  and  water. 

SEASONAL    HISTORY  AND  GENEBATIONS. 

Adults  as  well  as  partially  and  full  grown  larva?,  and  also  without 
doubt  the  pupae,  occur  in  many  fields  up  to  the  time  of  draining  for 
harvest.  With  late  crops  in  the  coast  region,  however,  and  in  the 
fields  of  Arkansas  on  account  of  the  difference  of  the  season  in  that 
State,  the  number  of  weevils  in  all  these  stages  diminishes  about  the 
time  when  the  plants  begin  to  head  in  the  latter  part  of  August. 
Weevils  found  in  fields  after  the  drawing  off  of  water  to  permit 
harvesting  are  apt  to  be  freshly  emerged  individuals  of  a  new  gen- 
eration. From  a  collection  of  infested  roots  obtained  by  Mr.  Pierce 
at  Beaumont,  Tex.,  June  28,  1904,  adults  emerged  as  early  as  July  2 
following.  In  case  such  early  emerged  weevils  breed  at  once,  they 
have  a  chance  to  produce  a  second  generation  in  a  season,  provided 
they  find  late  flooded  fields  or  suitable  water  holes.  At  Stuttgart, 
Ark.,  on  September  12,  Mr.  Hood  found  roots  of  rice  infested  by  a 
few  larvae  which  he  regarded  as  representatives  of  a  second  genera- 
tion. The  last  larva  found  by  the  writer  during  his  stay  at  Crow- 
ley, La.,  was  taken  September  25.  While  the  weevils  that  emerge  in 
July  possihhy  lay  eggs  for  a  second  generation,  the  species  is  prin- 
cipally propagated  in  one  yearly  generation. 

In  the  spring,  before  many  of  the  rice  fields  were  flooded.  Mr.  Hood 
collected  adults  on  grasses  and  red  rice  growing  in  ditches  and  other 
places  containing  water.  Since  the  weevils  have  not  been  known  to 
breed  in  such  places  until  the  soil  and  water  become  sufficiently  warm, 
at  which  time  the  flooding  of  rice  fields  is  well  under  way.  the  deduc- 
tion is  made  that  low  temperatures  up  to  this  time  exert  a  restrictive 
influence  upon  breeding. 

Examination  of  roots  of  red  rice  and  other  plants  "rowing  in  a 
constantly  flooded  ditch  at  Crowley.  La.,  on  October  •'>.  failed  to  dis- 
close any  evidences  of  infestation  :il  the  time.  These  results  -how 
conclusively  that  the  weevil  docs  not  breed  at  this  lime  of  year  even 
in  most  favorable  situations.  Not  only  were  the  adults  absent,  but 
the  hick  of  feeding  scars  on  the  leaves  denoted  that  they  had  not 
visited  there  for  some  time. 


THE    RICE    w  \  PER   WEEVIL. 


11 


The  fad  thai  adults  live  throughout  the  greater  pari  of  the  season 
has  beer  demonstrated  several  times.  In  an  experiment  with  speci- 
mens collected  at  Mackay,  Tex.,  April  5,  L904,  Mr.  W.  W.  Yothers 
succeeded  in  keeping  the  weevils  alive  by  furnishing  grass  for  food 
until  after  the  middle  of  duly.  Weevils  confined  on  rice  plants  by 
Mr.  Hood  at  Crowley,  La.,  duly  IS.  lived  later  than  the  middle  of 
September,  and  the  writer  has  made  a  corresponding  record  cover- 
ing a  period  from  July  11  to  September  21. 

The  common  absence  if  not  scarcity  of  fresh  signs  of  feeding  by 
adult-  late  in  the  season  or  at  the  time  when  the  new  generation  of 
weevils  is  expected  to  emerge  throws  much  doubl  on  the  question  of 
their  taking  any  food  then.  At  least  they  do  not  remain  long  on  the 
plants,  and  the  few  feeding  -ear-  that  may  appear  to  have  originated 
at  the  time  are  likely  produced  by  lingering  adult-  of  the  old  gen- 
eration. A  yearly  overlapping  of  generations  in  the  adult  stage  evi- 
dently occurs.  Few  specimens  thai  might  be  regarded  as  freshly 
emerged  weevil-  have  been  found  in  the  fields.  These  were  taken  by 
Mr.  I  Iood.  hiding  in  the  cracks  of  the  ground  a  fter  the  water  had  I  ieen 
drained  from  the  held  for  harvesting.  Possibly  some  of  these  weevils 
stray  to  electric  lights  at  night,  my  last  capture  of  a  weevil  being 
made  on  the  nighl  of  September  20.  If  a  new  generation  of  weevils 
occurs  no  evidence  of  it  has  been  found.  The  question  is.  What  be 
conies  of  them  until  they  go  into  hibernation  \ 

HIBERN  eriON.1 

During  the  fall  and  water  of  1910  Mr.  Hood  made  examinations 
of  various  places  which  might  serve  as  hibernating  quarters.  The 
materials  examined  included  rice  stubble,  loose  dirt  in  the  held-. 
straw-tacks  (both  old  and  new),  grass  and  other  vegetable  matter 
along  le\ee-.  ;:ud  Spanish  moss.  No  weevil-  were  found  hibernating 
except  in  the  Spanish  moss,  which,  however,  afforded  an  excellent 
shelter,  as  the  following  tabulated  observations  made  at  Crowley, 
La.,  will  show : 

Observations  on   the  places  of  hibernation   of  the   rice  water-weevil. 


Oct.  26.. 
Nov.  19. 

Dec.2... 


Date  m'  exam] 


Moss 
examined. 


1 
1) 


Distance 
nearest 


ground. 


Number 

of  w  eevils 

found. 


number  of 
per  ton 


1.464 


1  Wit  i   few  remarks,  all  of  the  notes  on  hiberi  the  weevils 

must  be  credited  t<>  Mr.  Hood,  who  has  made  the  most  extensive  Investigate 

■  IT   mile). 


12  THE    RICE    WATER-WEEVIL. 

As  indicated  by  the  preceding  table,  several  thousand  weevils  may 
hibernate  in  the  moss  on  a  single  tree.  The  appearance  of  large 
numbers  of  weevils  in  rice  fields  when  they  are  first  flooded  has  led 
to  the  opinion  that  the  pest  completes  one  generation  on  host  plants 
other  than  rice  before  this  time.  But  as  already  pointed  out,  no 
evidence  has  been  secured  that  will  sustain  this  view.  Abundance  of 
the  weevils  is  probably  due  to  their  successful  survival  through  the 
winter  and  emergence  from  hibernation. 

One  reference  in  literature  mentions  the  occurrence  of  adults  "  in 
wintertime  under  old  leaves  and  other  shelter  in  drier  pla<  es  near  the 
swamps."  The  finding  of  one  adult  in  litter  beneath  rich  stubble  is 
recorded  by  Mr.  D.  L.  Van  Dine  as  the  result  of  searching  for  half 
of  a  day  at  Stewart,  Tex.,  on  Octoher  28,  1909.  Entrance  into  hiber- 
nation is  probably  not  begun  much  before  the  time  when  the  nights 
are  cold  enough  for  frost.  Not  a  single  weevil  could  be  found  by 
the  writer  in  a  collection  of  Spanish  moss  obtained  on  September  29, 
at  Crowley,  La.,  and  in  the  preceding  spring  after  the  first  weevils 
appeared  Mr.  Hood  was  unable  to  find  any  specimens  remaining  in 
the  moss. 

NATURAL   ENEMIES. 

Besides  birds  no  enemy  is  known  to  feed  on  the  mature  weevils, 
although  the  snakes  and  frogs  which  frequent  the  fields  probably 
do  so.  Bird  droppings  found  by  Mr.  Hood  in  a  rice  field  at  Stutt- 
gart. Ark.,  on  September  12  consisted  largely  of  insect  remains,  those 
of  the  rice  water-weevil  being  the  most  abundant.  However,  two 
perfect  specimens  of  the  weevil  were  removed  from  the  droppings 
and  one  was  found  to  be  alive.  According  to  records  in  the  Biological 
Survey,  this  weevil  is  eaten  by  the  long-billed  marsh  wren  (Telma- 
todytes  palustris)   and  the  mallard  duck   (Anas  platyrhynchos) . 

Owing  to  their  concealment  in  mud  the  larva  and  pupa  are  secure 
from  enemies.  When  infested  roots  are  pulled  for  examination  and 
larva'  are  washed  out  any  minnows  that  happen  to  be  present  in  the 
water  will  greedily  snap  the  floating  bodies.  Predaceous  larva?  of 
v.atc;  beetles,  which  also  abound  in  flooded  fields,  struggle  with  one 
another  for  possession  of  a  weevil  larva.  If  these  predators  and  the 
several  kinds  of  rapacious  water  bugs  were  adapted  for  burrowing  in 
the  mud  and  reaching  the  rice  roots,  they  would  be  very  efficient 
oyers  of  both  weevil  larva?  and  pupae.  But  their  habit  of  hunt- 
ing in  the  open  -paces  of  water  renders  them  of  little  or  no  service 
against  the  weevil. 

METHODS  OF  CONTROL. 

UK  \l\l\i.   01    Till     FIELDS. 

A-  pointed  out  in  the  study  of  the  life  history,  the  existence  oi  the 

larva'  and  likewise  the  pupa'  depends  upon  a  saturation  of  the  soil. 


I  ill'.    RICE    WATER-WEEVIL.  13 

If  the  soil  dries  out  after  the  larvae  have  made  an  advance  in  growth, 
they  soon  die.     Tin-  practice  of  draining  fields  and  allowing  them 
to  dry  enough  to  cause  the  death  of  the  larvae  was  first  proposed  in 
1881  by  Col.  John  Screven,  a  rice  planter  in  South  Carolina,  and  was 
indorsed  by  Dr.  Howard  after  his  investigation  in  the  field  in  lvM. 
of  the  rice  growers  in  Louisiana  and  Texas  have  reported  good 
ts  from  periods  of  draining,  while  others  have  claimed  that  the 
plants  suffered  more  from  being  deprived   of  water  than   from   at- 
tacks.    Many  growers  therefore  advocate  deep  flooding  of  fields  as 
proper  treatment  of  rice  when  infested  by  the  weevil  larvae. 

Different  results  of  draining  are  mainly  accountable  to  the  ex 
of  damage  done  by  the  larva'  at  the  time  of  releasing  the  water. 
When  the  roots  have  been  hut  slightly  or  not  yet  severely  attacked, 
draining  seems  to  result  very  effectively  in  most  cases  by  the  reduc- 
tion of  the  number  of  larvae  to  a  minimum.  Effectiveness  depends 
on  the  length  of  time  that  plants  can  stand  -without  water  and  not 
suffer  from  the  want  of  it.  Plants  that  have  a  fair  hold  of  roots 
show  no  ill  effects  of  drying  spells  lasting  from  5  to  10  days  without 
rain.  In  case  of  heavy  rain,  drying  should  he  carried  on  for  some 
longer  or  until  the.  surface  of  the  ground  forms  a  dry  crust  and 
begins  to  crack.    This  f  drying  has  been  found  very  effective  in 

causing  the  death  of  larva-,  and  the  ground  has  still  retained  sufficient 
■  -ire  below  the  surface  to  sustain  the  plants  that  possessed  a  large 
proportion  of  root-. 

On  the  other  hand,  when  roots  have  become  severely  pnmed.  the 
plants  are  unable  to  endure  draining  without  being  further  impaired. 
Instead,  they  need  a  plentiful  supply  of  water  in  order  that  new  roots 
can  he  put  out  and  growth  resumed.  The  value  of  draining  is  de- 
pendent upon  the  enforcement  of  the  practice  at  the  proper  time, 
which  the  grower  can  easily  determine  by  making  examinatioi 
the  roots.  Many  growers  object  to  draining  on  account  of  the  • 
of  water  and  the  risk  or  difficulty  of  getting  fields  promptly  flooded 
again.  If  fields  were  so  arranged  that  water  could  be  turned  from 
one  to  another  in  succession  or  from  early  to  late  plantings,  most  of 
the  i  >uld  he  utilized  and  the  saving  in  the  cost  of  pumping, 

where  this  mean-  of  supply  is  employed,  would  he  an  item  of  coi 
eration.    Other  benefits  arising  from  change  ter  will  be  men- 

tioned later.     Continuance  of  flooding  to  enabl<  nine 

inpirv  by  larva-,  instead  of  taking  steps  to  destroy  the  .  will. 

a-   Mr.  Newell  has  inferred,  probably  lead  t<>  a  regular  in 
the  number  of  weevils  until  the  point   i-  reached  where,  the   ii 
will  make  profitable  rice  culture  impossible.    Coi 

loes  not   in  the  least  inconvenience  the  Ian  ondi- 

even  more  favorable  for  them.    Being  the  most  practical  method 
of  controlling  the  weevils,  draining  of  field-  .3  highly  im- 

portant 


14  THE   EICE   WATER-WEEVTL. 

RESULTS   OF  DRAINING. 

Conclusive  observations  upon  tests  of  draining  conducted  by  the 
writer  or  under  his  instructions  during  the  season  of  1911  are  pre- 
sented in  the  following  statements. 

At  Crowley.  La.,  en  June  9,  a  rice  grower  drained  some  parts  of 
his  field  of  early  planted  Honduras  rice  in  which  fully  one-fifth  of  the 
plants,  then  at  a  height  of  15  to  Is  inches^  showed  yellow  blades. 
The  roots  had  been  rather  severely  pruned,  but  enough  remained 
together  with  newly  grown  ones  to  permit  draining  with  safetv. 
As  many  as  six  and  seven  larva?  infested  the  roots  of  a  stool.  Reflood- 
ing  was  effected  June  19,  after  a  period  of  drying  which  had  lasted 
nearly  10  days.  Quite  a  noticeable  difference  existed  between  the 
drained  and  undrained  rice  on  July  21.  The  plants  in  the  drained 
areas  had  nearly  all  headed  out  uniformly,  while  most  of  the  un- 
drained  rice  was  behind  in  growth,  either  not  having  headed  or  hav- 
ing heads  just  formed  and  blooming.  Regarding  recovery,  the  ownei 
said  that  the  plants  which  grew  in  the  fresh  water  after  reflooding 
soon  lost  their  yellow  color  and  took  on  a  vigorous  growth  of  healthy 
green,  but  in  the  undrained  parts  with  standing  water  the  plants  re- 
covered much  more  slowly.  At  harvest  time  the  owner  estimated 
his  best  yield  on  land  that  had  been  drained  to  check  the  weevil 
larvae. 

In  the  field  of  another  grower,  however,  results  were  not  so  suc- 
cessful. These  small  young  plants  were  not  injured  badly  and 
showed  only  incipient  spots  and  streaks  of  weak  yellow  color.  This 
was  a  variety  of  Japan  rice.  The  field  was  drained  May  29  and  re- 
flooded  June  8,  giving  a  drying  of  10  days.  One  week  after  reflood- 
ing the  plants  had  taken  on  a  fresh  green  color,  and  the  infestation  of 
the  most  injured  roots  had  been  reduced  to  a  minimum,  as  shown 
by  the  nearly  normal  growth.  Owing  evidently  to  a  second  infesta- 
tion, during  which  no  draining  was  done,  an  irregular  belated  growth 
was  displayed  at  heading  time.  Whether  the  outcome  might  have 
been  worse  without  any  draining  can  only  be  surmised. 

Acting  under  a  cooperative  agreement.  Mr.  C.  G.  Haskell  reported 
some  very  important  results  of  his  examinations  at  Almyra.  Ark. 
On  draining  a.  field  July  20  In-  found  25  larva'  on  the  roots  of  25 
sfools.  On  flooding  the  field  July  28  he  found  only  two  larvae  on  the 
same  number  of  roots.  The  result  was  accomplished  by  eight  days  ^<( 
draining  and  drying.  A  stool  usually  produced  live  stalks  or  stems. 
By  calculating  percentage-  of  infestation  according  to  the  number  of 
stalks  the  draining  must  have  reduced  the  proportion  of  larva'  from 
20  pel-  cent  to  L.6  per  cent. 

Again,  on  draining  a  field  July  25  Mr.  Haskell  found  50  larvae  on 
the  roots  of  25  stools,  hut  on  reflooding  the  field  July  31  he  found  no 
more  than  9  larva'  per  25  stools.    The  draining  and  drying  therefore 


I  II  I.    RICE    W  A  I  EB   WEEVIL.  15 

lasted  six  days,  and  calculating  on  ;i  brsis  of  five  stalks  to  a  stool  the 
tation  was  reduced  from  10  to  7.2  ] >•■  r  cent.  The  writer's  own 
examination  of  this  rice  on  August  I.  the  second  day  of  refiooding, 
gave  substantial  evidence  of  the  reduction  of  larvae  in  corresponding 
numbers,  the  count  resulting  in  3  larvae  on  the  roots  of  10  stalks. 

Ai  Pine  Bluff,  Ark.,  on  August  5  the  writer  made  examinations 
in  a  rice  field  that  had  been  drained  for  five  days.  On  the  roots  of 
I",  stalks  only  nine  larvae  were  found  alive.  The  infestation  there- 
fore amounted  to  approximately  9  per  cent.  The  owner  stated  that 
before  draining  two  and  three  larva?  occurred  on  a  -tool.  Calculating 
five  stalks  per  stool,  the  infestation  then  could  nol  have  been  less  than 
33  per  cent.  In  sonic  places  the  ground  was  still  saturated,  but  most 
of  it  was  stiff  mud.  Thai  the  draining  really  caused  a  reduction  in 
the  number  of  larvae  by  death  was  evidenced  by  the  finding  of  two 
dead  ones,  and  some  of  the  live  ones  seemed  weak  as  if  about  ready  to 
die.  Not  many  roots  were  badly  cut  and  the  draining  began  at  an  opi 
portune  time.  The  pumping  of  water  on  this  Held  was  resumed 
August  8,  but  ii  was  not  wholly  Hooded  until  a  few  days  later.  The 
drying  covered  seven  days  at  least.  No  rain  fell  during  this  time, 
and  the  ground  had  begun  to  crack  from  drying.  The  results  were 
considered  very  beneficial,  as  the  larvae  caused  no  further  trouble  and 
the  rice  headed  out    splendidly. 

EFFECTS    in     RUNNING    WATEE. 

Direct  observations,  as  well  as  the  testimony  of  growers,  I 
brought  out  the  fact  that  rice  growing  in  running  water  suffers  little 
from  weevil  attack-.  In  these  cases,  however,  no  considerable  area 
ha-  yet  he. mi  -ecu  in  which  the  water  flowed  with  any  perceptible  cur- 
rent. To  maintain  a  distinct  moving  Hood  over  a  large  field  would 
require  an  immense  supply  of  water.  The  instance-  that  have  been 
observed  were  confined  i"  -pot-  or  -mall  plat-  covered  by  the  inflow 
of  water  from  ;i  canal  or  ditch.  In  spreading  onto  a  Held  from  an 
inlet  the  current  soon  loses  fop-,,  and  any  low  temperature.  Where 
;i  cool  How  of  water  i-  pumped  from  a  well  directly  onto  a  Held  the 
low  temperature  seems  to  exert  n  controlling  factor  against  infesta- 
ticn.  But  these  cases  arc  rare,  because  the  rice  demands  warm  tem- 
peratures for  vigorous  growth,  and  the  -un  heat  greatly  restricts  the 
1   area. 

EFFECTS  01     DEEP    IND  SHALLOW     I  NO  AND  STAGNATION. 

Deep  water  ami  stagnant  water  greatly  favor  development 
weevil-.  A-  already  pointed  out,  rice  in  -pot-  or  areas  of  deep  0 
ing   i-   most    severely   attacked.     Severity   of   attacks    i-   especially 


16  CHE    RICE    WATER-WEEVIL. 

marked  in  shallow  water  almost  as  much  as  in  deep  water  when 
either  heroines  stagnant.  In  a  field  that  had  received  only  a  scant 
supply  of  water,  which  in  fact  merely  filled  the  low  places  although 
keeping  all  of  the  ground  soaked,  very  few  larva'  could  be  found. 
Most  of  these  larva?  occurred  on  roots  of  weak  plants  in  the  pools, 
while  the  best  growth  stood  out  of  water  and  was  scarcely  attacked 
at  all.  Soaking  instead  of  flooding  appeared  to  result  very  bene- 
ficially, not  only  controlling  infestation  but  inducing  prime  growth  of 
plants  at  least  past  the  stage  "of  stooling  when  the  coarse  leaves  offer 
little  attraction  to  the  weevils. 

EFFECTS    OF    EARLY,    DELAYED,    AND    LATE    FLOODIMi. 

Rice  in  different  fields  that  were  first  flooded  at  various  times 
covering  a  seasonal  range  of  dates  in  accordance  with  the  planting 
and  sprouting  has  in  due  course  been  found  subjected  to  the  same 
degree  of  infestation.  No  advantage  can  he  gained  against  the  weevil 
by  choosing  any  particular  time  for  flooding  that  will  still  be  suit- 
able for  the  needs  of  the  plants.  An  attempt  to  delay  full  flooding 
by  a  gradual  soaking  of  fields  in  order  that  the  plants  might  attain 
a  strong  growth  and  be  able  to  withstand  or  escape  attacks  after 
deep  water  was  applied  met  with  interference  from  heavy  rainfalls 
which  flooded  the  fields,  and  the  owner  then  saved  the  water.  The 
probable  effectiveness  of  soaking  is  indicated  by  the  case  of  accidental 
shortage  of  water,  as  mentioned  in  the  preceding  subject. 

EFFECTS     OF    ALTERNATE     FLOODING     AM)    DRYING. 

At  Crowley,  La.,  on  June  28,  inspection  was  made  of  a  field  of  rice 
that  had  been  allowed  to  dry  out  from  stoppage  of  water  supply  on 
two  occasions,  one  lasting  six  days  and  the  other  four  days.  The  oc- 
currence of  larvae  was  limited  principally  to  the  most  heavily  flooded 
parts,  and  the  roots  of  the  plants  were  not  badly  injured.  The  com- 
parative scarcity  of  the  larvae  throughout  the  field  was  attributed  to 
the  effects  of  the  two  intervals  of  drying,  and  the  rice  escaped  much 
danger  from  attacks. 

At  Almyra.  Ark.,  on  August  1.  other  observations  were  made  on  a 
field  where  scarcity  of  water  had  caused  alternate  periods  of  drying. 
Water  had  been  supplied  but  little  more  than  half  of  the  time  since 
first  Hooding,  though  the  ground  had  been  generally  kept  damp  with 
the  addition  of  rainfall.  No  larvae  were  found  on  the  roots  of  this 
rice,  and  Only  a  few  weevils  occurred  on  weak  plants  near  1  he  edges 
of  the  field.  The  plants  exhibited  a  high,  vigorous,  and  fairly 
healthy  growth,  the  laclc  of  enough  water  having  evidently  resulted 
in   a   yellow   tinge  of   the   leaves,   which,   however,    promised   to   be 


BK  i     w  \  I  i  i:  w  EEVTL. 


17 


speedily  overcome   owing  to   flooding  rains.     The  crop  eventually 
produced  an  excellent  yield. 

1M      (H      FERTILIZERS      \NI>     APPLICATION     OF     LIME. 

In  an  experiment  to  determine  whether  the  use  of  fertilizers  and 
application  of  lime  would  serve  as  a  check  on  weevil  infestation,  plats 
for  growing  rice  were  prepared  at  Crowley.  La.,  as  shown  by  the 
accompanying  diagram,  which  also  gives  the  results  of  examinations 
on  July  8.  The  whole  field  was  flooded  equally  to  an  average  depth 
of  G  inches.  The  arrangement  and  treatment  of  the  plat-  and  status 
of  infestation  are  outline. I  as   follow-: 


Unlimed. 


Unlimcd. 


Limed.  2.000 

iiounils  [.or 

acre. 


Checks 

;>  larva 

-'alks. 

1  larva. 

11  la: 

Acid   pi                               inds,    10   per 

7  larva 

:alks. 

C  larva  . 

Acid  phosphate  m<  above  i>lus  muriate 
oi  potash,  60  pounds  per  acre 

11  larvi 

-:alks. 

9  larva-. 

7  lar 

Total  proportionate  number  of  larvae: 

For  the  cheek  plat 17.  or  22jj  per  cent  infestation. 

For  the  phosphate  plat 19,  or  l'.v.  per  ceul  infestation. 

For  the  phosphate  and  potash  plal 30,  or  10  per  cent  infestation. 

Calculating  another  way  from  the  foregoing  outline,  the  limed 
areas  were  found  to  have  ■_'!  larvae  compared  with  1G  larva'  in  the 
unlimed  areas  of  the  same  plat,  while  in  the  opposite  plat  26  larvae 
were  taken  on  the  roots  of  <  be  same  number  of  sta  Iks. 

No  advantage  in  reducing  or  retarding  infestation  appeared  to  be 
shown  through  the  application  of  fertilizer-  or  lime  to  the  soil,  bul 
rather  the  contrary  effects  are  indicated,  as  the  strip  with  double 
fertilization  contained  the  mosl  larvae.  Since  the  plant  growth  had 
responded  in  proportion  to  the  d<  :  fertilization,  the  stimulated 

plants  exhibited  uo  signs  of  injury  resulting  in  yellow  appearance  of 
Leaves  except  in  the  limed  areas,  which  a>  a  whole  included  the 
poorest  growth  on  account  of  the  severer  pruning  of  the  small  root 
systems. 

Further  observations  made  at  Midland.  La.,  have  led  to  the  con- 
clusion that  fertilization  doc-  uot  prevent  nor  even  hinder  the  pro- 
pagation of  larvae,  but  the  extra  nourishment  may  assist  the  plants 
to  overcome  attacks. 


18  THE    BICE    WATER-WEEVIL. 

USE    OF    TRAP    LIGHTS    FOR    ADULTS. 

The  appearance  of  adults  at  artificial  lights  at  night  has  suggested 
the  plan  of  placing  lights  in  the  fields  and  trapping  the  weevils  which 
may  be  attracted.  Great  numbers  of  the  weevils  seek  the  electric  lights 
of  stores  in  the  towns  throughout  regions  where  the  insects  abound. 
( )rdinary  lights  in  dwellings  are  sometimes  frequented.  At  Crowley. 
La.,  more  than  a  hundred  weevils  have  been  collected  within  a  few 
minutes  on  a  single  store  window.  They  appear  most  numerously 
on  warm  dark  nights,  but,  like  many  other  insects,  they  do  not  fly  to 
lights  in  any  considerable  number  when  the  moon  shines.  Neither 
does  the  time  of  their  flight  seem  to  last  long,  for  as  soon  as  dark- 
ness has  settled,  most  of  them  come  in  a  rush,  and  only  occasionally 
do  stragglers  show  themselves  later  in  the  night.  Their  seasonal 
appearance  begins  from  the  1st  to  the  middle  of  April,  and  about  the 
middle  of  August  they  become  very  scarce. 

Tests  of  the  efficiency  of  light  as  a  practical  means  of  attraction 
were  conducted  at  Crowley.  A  portable  acetylene  outfit  was  used  to 
furnish  light,  being  operated  near  rice  fields  1  mile  from  town.  Some 
of  the  best  results  were  as  follows,  the  weevils  being  taken  on  a 
cloth  screen  that  was  provided  for  the  purpose  of  inducing  them  to 
alight : 

On  the  night  of  May  26,  1910,  Mr.  Van  Dine  started  the  light  at 
8  o'clock  and  captured  over  40  weevils  in  the  first  15  minutes.  Later 
the  breeze  increased  and  only  strong  flying  insects  came  to  the  light. 

Starting  the  light  at  8  o'clock  on  July  19,  after  a  day  of  heavy 
rains.  Mr.  Hood  collected  - 1  weevils  in  45  minutes.  But  on  the  night 
of  July  29,  which  was  clear  and  warm  with  slight  south  breeze,  be 
placed  the  light  in  the  middle  of  a  rice  field  and  caught  12.")  weevils 
between  8  and  9  o'clock. 

SUGGESTIONS   FOB   PROTECTIVE  TREATMENT. 

POISON'I.M,    ADULTS. 

When  the  weevils  gather  in  particular  portions  of  a  rice  field,  as 
they  often  do  along  deeply  flooded  edges,  dead  furrows,  and  in  spots, 
opportunities  seem  to  be  presented  whereby  the  application  of  a  food 
poison  could  be  made. effective.  As  the  weevils  indulge  in  rather  ex- 
tensive feeding  compared  with  their  size,  the  poisoning  of  the 
plants  would  be  apt  to  cause  the  death  of  great  numbers  of  the  adults 
that  might  feed  upon  the  poisoned  leaves.  The  application  of  the 
poison  should  be  made  upon  the  first  appearance  of  the  insects  before 
they  have  had  much  chance  to  oviposit.  The  poison  must  be  selected 
with  reference  to  its  safety  on  the  plants,  and  if  in  the  form  of  a 
powder,  it  could  be  easily  distributed  by  means  of  a  dust  gun.  from 


I  in     BK  i     w  \  i  t  t;  w  EE\  l!,.  19 

which  it  mighl  be  spread  for  some  distance  by  wind.  Probably  the 
only  danger  would  be  to  live  stock  having  access  to  the  water  the 
drinking  of  which  would  be  a  remote  possibility. 

i  I    I   1  I   i:  \1      MANAGEMENT. 

Clean  cultural  management  in  dealing  with  the  weevil  as  with 
other  crop  pests  is  advisable.  By  restricting  the  growth  of  the 
various  grasses  and  other  plant-,  particularly  the  objectionable  red 
variety  of  rice,  which  grow  along  and  within  canals,  ditches,  and 
water  boles,  much  advantage  could  be  derived  toward  the  suppression 
of  the  breeding  of  the  weevils  on  the  uncultivated  host  plants.  Drain- 
age of  bayous,  sinks,  and  water  hole-  would  doubtless  be  of  great 
benefit  for  the  control  of  the  weevil  alone. 

Leveling  of  the  surface  of  fields  that  are  to  be  planted  in  rice  and 
plow  ing  in  such  a  manner  as  to  avoid  dead  furrows  as  much  as  | 
hie  would  obviate  many  of  the  depressions  which  on  being  deeply 
flooded  conduce  to  a  high  infestation  of  the  plants  in  such  place-. 

Finally,  a  thorough  preparation  of  the  -oil  before  planting  is  to  he 
recommended,  in  order  that  grass  and  weed-  ma\  he  eradicated  with- 
out the  necessity  of  deep  flooding  for  the  purpose  of  drowning  them. 
Thi.-  will  permit  very  -hallow  flooding  with  periods  of  draining  or 
mere  soaking  of  fields  for  the  control  of  infestation  and  the  better- 
ment of  the  crops. 

-I    M  M  \KY. 

The   rice   water-weevil  causes  more  damage  to   rice   crops   in   the 
Southern  State-  than  any  other  insect  affecting  rice  plant-.     When  it 
is  in  the  larva]  stage  it  commit-  severe  injuries  to  rice  plant-  by  de 
stroying  the  root-.     Some  harm  i-  done  by  the  adult-  in  feeding  on 
the  leaves. 

The  insect  chooses  food  plants  that  grow  in  wet  places  and  it 
breeds  only  where  it  finds  water.  Eggs  are  evidentlj  laid  on  root-  in 
water  or  mud.  under  which  condition-  tin'  larvae  hatch,  feed,  grow, 
and  transform  into  pupae,  and  finally  the  adult-  mature  and  emerge. 

Two  generations  may  possibly  be  produced  in  a  season,  hut  one 
generation  seems  to  he  the  rule.  Adults  pas-  the  winter  in  hiberna- 
tion, appearing  in  spring  and  invading  the  rice  held-. 

The  most  practical  means  of  controlling  the  weevil  consists  in  the 
practice  of  draining  and  allowing  infested  rice  fields  to  dry  suffi- 
ciently at  tic  propel-  time  or  before  the  attacks  of  larvae  have  greatly 
weakened  the  plants.  Alternate  flooding  and  drying,  if  carried  out 
properly,  will  accomplish  the  same  results.  Very  -hallow  flooding 
or  soaking  of  fields  re-train-  infestation.  Fertilization  assists  the 
plants  to  overcome  injury. 


20 


THE    RICE    WATER-WEEVIL. 


Considerable  numbers  of  weevils  can  be  captured  at  lights  and 
destroyed,  and  the  possibility  of  poisoning  them  in  fields  needs  to  be 
put  to  the  test.  Cultural  management  should  be  directed  with  the 
view  of  enforcing  every  advantage  against  the  weevil  that  will  be 
consistent  with  the  welfare  of  the  crop. 

Approved: 

James  Wilson, 

Secretary  of  Agrit  uZture, 
Washington,  D.  C,  April  12,  1912. 


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